<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>烟花动画特效</title>
 
<style>
html,body{
	margin:0px;
	width:100%;
	height:100%;
	overflow:hidden;
	background:#000;
}
 
#canvas{
	width:100%;
	height:100%;
}
</style>
 
</head>
<body>
 
<canvas id="canvas"></canvas><script>
function initVars(){
 
	pi=Math.PI;
	ctx=canvas.getContext("2d");
	canvas.width=canvas.clientWidth;
	canvas.height=canvas.clientHeight;
	cx=canvas.width/2;
	cy=canvas.height/2;
	playerZ=-25;
	playerX=playerY=playerVX=playerVY=playerVZ=pitch=yaw=pitchV=yawV=0;
	scale=600;
	seedTimer=0;seedInterval=5,seedLife=100;gravity=.02;
	seeds=new Array();
	sparkPics=new Array();
	s="https://cantelope.org/NYE/";
	for(i=1;i<=10;++i){
		sparkPic=new Image();
		sparkPic.src=s+"spark"+i+".png";
		sparkPics.push(sparkPic);
	}
	sparks=new Array();
	pow1=new Audio(s+"pow1.ogg");
	pow2=new Audio(s+"pow2.ogg");
	pow3=new Audio(s+"pow3.ogg");
	pow4=new Audio(s+"pow4.ogg");
	frames = 0;
}
 
function rasterizePoint(x,y,z){
 
	var p,d;
	x-=playerX;
	y-=playerY;
	z-=playerZ;
	p=Math.atan2(x,z);
	d=Math.sqrt(x*x+z*z);
	x=Math.sin(p-yaw)*d;
	z=Math.cos(p-yaw)*d;
	p=Math.atan2(y,z);
	d=Math.sqrt(y*y+z*z);
	y=Math.sin(p-pitch)*d;
	z=Math.cos(p-pitch)*d;
	var rx1=-1000,ry1=1,rx2=1000,ry2=1,rx3=0,ry3=0,rx4=x,ry4=z,uc=(ry4-ry3)*(rx2-rx1)-(rx4-rx3)*(ry2-ry1);
	if(!uc) return {x:0,y:0,d:-1};
	var ua=((rx4-rx3)*(ry1-ry3)-(ry4-ry3)*(rx1-rx3))/uc;
	var ub=((rx2-rx1)*(ry1-ry3)-(ry2-ry1)*(rx1-rx3))/uc;
	if(!z)z=.000000001;
	if(ua>0&&ua<1&&ub>0&&ub<1){
		return {
			x:cx+(rx1+ua*(rx2-rx1))*scale,
			y:cy+y/z*scale,
			d:Math.sqrt(x*x+y*y+z*z)
		};
	}else{
		return {
			x:cx+(rx1+ua*(rx2-rx1))*scale,
			y:cy+y/z*scale,
			d:-1
		};
	}
}
 
function spawnSeed(){
	
	seed=new Object();
	seed.x=-50+Math.random()*100;
	seed.y=25;
	seed.z=-50+Math.random()*100;
	seed.vx=.1-Math.random()*.2;
	seed.vy=-1.5;//*(1+Math.random()/2);
	seed.vz=.1-Math.random()*.2;
	seed.born=frames;
	seeds.push(seed);
}
 
function splode(x,y,z){
	
	t=5+parseInt(Math.random()*150);
	sparkV=1+Math.random()*2.5;
	type=parseInt(Math.random()*3);
	switch(type){
		case 0:
			pic1=parseInt(Math.random()*10);
			break;
		case 1:
			pic1=parseInt(Math.random()*10);
			do{ pic2=parseInt(Math.random()*10); }while(pic2==pic1);
			break;
		case 2:
			pic1=parseInt(Math.random()*10);
			do{ pic2=parseInt(Math.random()*10); }while(pic2==pic1);
			do{ pic3=parseInt(Math.random()*10); }while(pic3==pic1 || pic3==pic2);
			break;
	}
	for(m=1;m<t;++m){
		spark=new Object();
		spark.x=x; spark.y=y; spark.z=z;
		p1=pi*2*Math.random();
		p2=pi*Math.random();
		v=sparkV*(1+Math.random()/6)
		spark.vx=Math.sin(p1)*Math.sin(p2)*v;
		spark.vz=Math.cos(p1)*Math.sin(p2)*v;
		spark.vy=Math.cos(p2)*v;
		switch(type){
			case 0: spark.img=sparkPics[pic1]; break;
			case 1:
				spark.img=sparkPics[parseInt(Math.random()*2)?pic1:pic2];
				break;
			case 2:
				switch(parseInt(Math.random()*3)){
					case 0: spark.img=sparkPics[pic1]; break;
					case 1: spark.img=sparkPics[pic2]; break;
					case 2: spark.img=sparkPics[pic3]; break;
				}
				break;
		}
		spark.radius=25+Math.random()*50;
		spark.alpha=1;
		spark.trail=new Array();
		sparks.push(spark);
	}
	switch(parseInt(Math.random()*4)){
		case 0:	pow=new Audio(s+"pow1.ogg"); break;
		case 1:	pow=new Audio(s+"pow2.ogg"); break;
		case 2:	pow=new Audio(s+"pow3.ogg"); break;
		case 3:	pow=new Audio(s+"pow4.ogg"); break;
	}
	d=Math.sqrt((x-playerX)*(x-playerX)+(y-playerY)*(y-playerY)+(z-playerZ)*(z-playerZ));
	pow.volume=1.5/(1+d/10);
	pow.play();
}
 
function doLogic(){
	
	if(seedTimer<frames){
		seedTimer=frames+seedInterval*Math.random()*10;
		spawnSeed();
	}
	for(i=0;i<seeds.length;++i){
		seeds[i].vy+=gravity;
		seeds[i].x+=seeds[i].vx;
		seeds[i].y+=seeds[i].vy;
		seeds[i].z+=seeds[i].vz;
		if(frames-seeds[i].born>seedLife){
			splode(seeds[i].x,seeds[i].y,seeds[i].z);
			seeds.splice(i,1);
		}
	}
	for(i=0;i<sparks.length;++i){
		if(sparks[i].alpha>0 && sparks[i].radius>5){
			sparks[i].alpha-=.01;
			sparks[i].radius/=1.02;
			sparks[i].vy+=gravity;
			point=new Object();
			point.x=sparks[i].x;
			point.y=sparks[i].y;
			point.z=sparks[i].z;
			if(sparks[i].trail.length){
				x=sparks[i].trail[sparks[i].trail.length-1].x;
				y=sparks[i].trail[sparks[i].trail.length-1].y;
				z=sparks[i].trail[sparks[i].trail.length-1].z;
				d=((point.x-x)*(point.x-x)+(point.y-y)*(point.y-y)+(point.z-z)*(point.z-z));
				if(d>9){
					sparks[i].trail.push(point);
				}
			}else{
				sparks[i].trail.push(point);
			}
			if(sparks[i].trail.length>5)sparks[i].trail.splice(0,1);				
			sparks[i].x+=sparks[i].vx;
			sparks[i].y+=sparks[i].vy;
			sparks[i].z+=sparks[i].vz;
			sparks[i].vx/=1.075;
			sparks[i].vy/=1.075;
			sparks[i].vz/=1.075;
		}else{
			sparks.splice(i,1);
		}
	}
	p=Math.atan2(playerX,playerZ);
	d=Math.sqrt(playerX*playerX+playerZ*playerZ);
	d+=Math.sin(frames/80)/1.25;
	t=Math.sin(frames/200)/40;
	playerX=Math.sin(p+t)*d;
	playerZ=Math.cos(p+t)*d;
	yaw=pi+p+t;
}
 
function rgb(col){
	
	var r = parseInt((.5+Math.sin(col)*.5)*16);
	var g = parseInt((.5+Math.cos(col)*.5)*16);
	var b = parseInt((.5-Math.sin(col)*.5)*16);
	return "#"+r.toString(16)+g.toString(16)+b.toString(16);
}
 
function draw(){
	
	ctx.clearRect(0,0,cx*2,cy*2);
	
	ctx.fillStyle="#ff8";
	for(i=-100;i<100;i+=3){
		for(j=-100;j<100;j+=4){
			x=i;z=j;y=25;
			point=rasterizePoint(x,y,z);
			if(point.d!=-1){
				size=250/(1+point.d);
				d = Math.sqrt(x * x + z * z);
				a = 0.75 - Math.pow(d / 100, 6) * 0.75;
				if(a>0){
					ctx.globalAlpha = a;
					ctx.fillRect(point.x-size/2,point.y-size/2,size,size);				
				}
			}
		}
	}
	ctx.globalAlpha=1;
	for(i=0;i<seeds.length;++i){
		point=rasterizePoint(seeds[i].x,seeds[i].y,seeds[i].z);
		if(point.d!=-1){
			size=200/(1+point.d);
			ctx.fillRect(point.x-size/2,point.y-size/2,size,size);
		}
	}
	point1=new Object();
	for(i=0;i<sparks.length;++i){
		point=rasterizePoint(sparks[i].x,sparks[i].y,sparks[i].z);
		if(point.d!=-1){
			size=sparks[i].radius*200/(1+point.d);
			if(sparks[i].alpha<0)sparks[i].alpha=0;
			if(sparks[i].trail.length){
				point1.x=point.x;
				point1.y=point.y;
				switch(sparks[i].img){
					case sparkPics[0]:ctx.strokeStyle="#f84";break;
					case sparkPics[1]:ctx.strokeStyle="#84f";break;
					case sparkPics[2]:ctx.strokeStyle="#8ff";break;
					case sparkPics[3]:ctx.strokeStyle="#fff";break;
					case sparkPics[4]:ctx.strokeStyle="#4f8";break;
					case sparkPics[5]:ctx.strokeStyle="#f44";break;
					case sparkPics[6]:ctx.strokeStyle="#f84";break;
					case sparkPics[7]:ctx.strokeStyle="#84f";break;
					case sparkPics[8]:ctx.strokeStyle="#fff";break;
					case sparkPics[9]:ctx.strokeStyle="#44f";break;
				}
				for(j=sparks[i].trail.length-1;j>=0;--j){
					point2=rasterizePoint(sparks[i].trail[j].x,sparks[i].trail[j].y,sparks[i].trail[j].z);
					if(point2.d!=-1){
						ctx.globalAlpha=j/sparks[i].trail.length*sparks[i].alpha/2;
						ctx.beginPath();
						ctx.moveTo(point1.x,point1.y);
						ctx.lineWidth=1+sparks[i].radius*10/(sparks[i].trail.length-j)/(1+point2.d);
						ctx.lineTo(point2.x,point2.y);
						ctx.stroke();
						point1.x=point2.x;
						point1.y=point2.y;
					}
				}
			}
			ctx.globalAlpha=sparks[i].alpha;
			ctx.drawImage(sparks[i].img,point.x-size/2,point.y-size/2,size,size);
		}
	}
}
 
function frame(){
 
	if(frames>100000){
		seedTimer=0;
		frames=0;
	}
	frames++;
	draw();
	doLogic();
	requestAnimationFrame(frame);
}
 
window.addEventListener("resize",()=>{
	canvas.width=canvas.clientWidth;
	canvas.height=canvas.clientHeight;
	cx=canvas.width/2;
	cy=canvas.height/2;
});
 
initVars();
frame();
</script>
 
</body>
</html>
